Indication position calculation system, indicator for indication position calculation system, game system, and indication position calculation method

ABSTRACT

An imaging section successively outputs light-reception information relating to each pixel from a starting pixel SP to an end pixel EP, the starting pixel SP being provided on one end of an image PC acquired by the imaging section and the end pixel EP being provided on the other end of the image PC. The imaging section is provided in an indicator so that the starting pixel SP is disposed on a lower side and the end pixel EP is disposed on an upper side when the indicator is held in a reference position.

Japanese Patent Application No. 2007-35228, filed on Feb. 15, 2007, ishereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to an indication position calculationsystem, an indicator for an indication position calculation system, agame system, and an indication position calculation method.

An indication position calculation system has been known whichcalculates an indication position of an indicator on an indication plane(e.g., monitor or screen), such as a shooting game system using agun-type controller or a presentation system using a pointing device. Insuch an indication position calculation system, an infrared light sourceor the like is disposed near the indication plane. The light source isimaged using an image sensor (light-receiving sensor) provided on theend of the indicator, and the indication position of the indicator iscalculated based on the position of the light-emitting section in theresulting image.

In such an indication position calculation system, accurate positioncalculations cannot be performed when the image sensor receives light(noise) other than light from the light source. A related-art indicationposition calculation system determines whether the light detected by theimage sensor is light from the light source or noise based on the lengthand the size of the light reception area detected by the image sensor.Japanese Patent No. 2961097 discloses such technology, for example.

According to a related-art indication position calculation system, sincethe processing load increases to determine whether the light detected bythe image sensor is light from the light source or noise, the indicationposition calculation speed decreases. Therefore, when the user of thesystem changes the direction of the indicator at high speed, thecalculation speed cannot follow the change in direction, whereby anaccurate indication position cannot be provided to the user.

SUMMARY

According to a first aspect of the invention, there is provided anindication position calculation system calculating an indicationposition of an indicator, the indication position calculation systemcomprising:

a light-emitting section;

an imaging section which is provided in the indicator, acquires an imageand successively outputs light-reception information of pixels of theacquired image, wherein one of the pixels having the light-receptioninformation output primarily is disposed on a lower side of the imageand another one of the pixels having the light-reception informationoutput last is disposed on an upper side of the image when the indicatoris held in a reference position;

a determination section which determines whether or not the pixels areeffective pixels satisfying a given condition based on thelight-reception information; and

a calculation section which performs position calculations based onidentification information of the effective pixels in order to obtainthe indication position of the indicator when light received by theeffective pixels is included in light emitted from the light-emittingsection,

the calculation section performing the position calculations based onthe identification information of a first effective pixel which is oneof the effective pixels and is primarily determined to satisfy the givencondition.

According to a second aspect of the invention, there is provided anindicator for an indication position calculation system, the indicatorcomprising:

an imaging section which acquires an image of a light emitting sectionand successively outputs light-reception information of pixels of theacquired image;

a determination section which determines whether or not the pixels areeffective pixels satisfying a given condition based on thelight-reception information; and

a calculation section which performs position calculations based onidentification information of the effective pixels in order to obtain anindication position of the indicator when light received by theeffective pixels is included in light emitted from the light-emittingsection,

the calculation section performing the position calculations based onthe identification information of a first effective pixel which is oneof the effective pixels and is primarily determined to satisfy the givencondition; and

the imaging section being provided in the indicator held in a referenceposition when one of the pixels having the light-reception informationoutput primarily is disposed on a lower side of the image and anotherone of the pixels having the light-reception information output last isdisposed on an upper side of the image.

According to a third aspect of the invention, there is provided a gamesystem calculating an indication position of an indicator, the gamesystem comprising:

a display section which displays an object;

a light-emitting section which has a given positional relationship withthe display section;

an imaging section which is provided in the indicator, acquires an imageand successively outputs light-reception information of pixels of theacquired image, wherein one of the pixels having the light-receptioninformation output primarily is disposed on a lower side of the imageand another one of the pixels having the light-reception informationoutput last is disposed on an upper side of the image when the indicatoris held in a reference position;

a determination section which determines whether or not the pixels areeffective pixels satisfying a given condition based on thelight-reception information; and

a calculation section which performs position calculations based onidentification information of the effective pixels in order to obtainthe indication position of the indicator when light received by theeffective pixels is included in light emitted from the light-emittingsection,

the calculation section performing the position calculations based onthe identification information of a first effective pixel which is oneof the effective pixels and is primarily determined to satisfy the givencondition.

According to a fourth aspect of the invention, there is provided anindication position calculation method comprising:

causing an imaging section provided in an indicator to acquire an imageof a light emitting section and successively output light-receptioninformation of pixels of the acquired image;

causing a determination section to determine whether or not the pixelsare effective pixels satisfying a given condition based on thelight-reception information; and

causing a calculation section to perform position calculations based onidentification information of the effective pixels in order to obtain anindication position of the indicator when light received by theeffective pixels is included in light emitted from the light-emittingsection,

the calculation section performing the position calculations based onthe identification information of a first effective pixel which is oneof the effective pixels and is primarily determined to satisfy the givencondition; and

the imaging section being provided in the indicator held in a referenceposition when one of the pixels having the light-reception informationoutput primarily is disposed on a lower side of the image and anotherone of the pixels having the light-reception information output last isdisposed on an upper side of the image.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagram schematically showing an example of the appearanceof a system according to one embodiment of the invention.

FIG. 2 is a diagram illustrating an example of an image acquiredaccording to one embodiment of the invention.

FIG. 3 is a diagram illustrating an example of an indicator and animaging section according to one embodiment of the invention.

FIG. 4A is a diagram illustrating an example of an installation state ofa system according to one embodiment of the invention, and FIG. 4B is adiagram illustrating an example of an image acquired according to oneembodiment of the invention.

FIG. 5 is a functional block diagram showing an example of an indicatoraccording to one embodiment of the invention.

FIG. 6 is a diagram illustrating an example of part of an image acquiredaccording to one embodiment of the invention.

FIG. 7 is a flowchart showing an example of a process according to oneembodiment of the invention.

FIG. 8 is a flowchart showing an example of a process according to oneembodiment of the invention.

FIG. 9 is a flowchart showing an example of a process according to oneembodiment of the invention.

FIGS. 10A and 10B are diagrams illustrating an example of the principleaccording to one embodiment of the invention.

FIGS. 11A and 11B are diagrams illustrating image examples acquiredaccording to one embodiment of the invention.

FIG. 12 is a diagram schematically showing an example of the appearanceof a light-emitting section according to one embodiment of theinvention.

FIG. 13 is a diagram schematically showing an example of the appearanceof a light-emitting section according to one embodiment of theinvention.

FIG. 14 is a diagram schematically showing an example of the appearanceof a light-emitting section according to one embodiment of theinvention.

FIGS. 15A and 15B are diagrams schematically showing an example of theappearance of a light-emitting section according to one embodiment ofthe invention.

FIG. 16 is a functional block diagram showing an example of anindication position calculation system according to one embodiment ofthe invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

The invention may provide an indication position calculation system, anindicator for an indication position calculation system, a game system,and an indication position calculation method capable of promptly andaccurately calculating an indication position with a reduced processingload.

(1) According to one embodiment of the invention, there is provided anindication position calculation system calculating an indicationposition of an indicator, the indication position calculation systemcomprising:

a light-emitting section;

an imaging section which is provided in the indicator, acquires an imageand successively outputs light-reception information of pixels of theacquired image, wherein one of the pixels having the light-receptioninformation output primarily is disposed on a lower side of the imageand another one of the pixels having the light-reception informationoutput last is disposed on an upper side of the image when the indicatoris held in a reference position;

a determination section which determines whether or not the pixels areeffective pixels satisfying a given condition based on thelight-reception information; and

a calculation section which performs position calculations based onidentification information of the effective pixels in order to obtainthe indication position of the indicator when light received by theeffective pixels is included in light emitted from the light-emittingsection, the calculation section performing the position calculationsbased on the identification information of a first effective pixel whichis one of the effective pixels and is primarily determined to satisfythe given condition.

According to one embodiment of the invention, there is provided anindicator for an indication position calculation system, the indicatorcomprising:

an imaging section which acquires an image of a light emitting sectionand successively outputs light-reception information of pixels of theacquired image;

a determination section which determines whether or not the pixels areeffective pixels satisfying a given condition based on thelight-reception information; and

a calculation section which performs position calculations based onidentification information of the effective pixels in order to obtain anindication position of the indicator when light received by theeffective pixels is included in light emitted from the light-emittingsection,

the calculation section performing the position calculations based onthe identification information of a first effective pixel which is oneof the effective pixels and is primarily determined to satisfy the givencondition; and

the imaging section being provided in the indicator held in a referenceposition when one of the pixels having the light-reception informationoutput primarily is disposed on a lower side of the image and anotherone of the pixels having the light-reception information output last isdisposed on an upper side of the image.

According to one embodiment of the invention, there is provided anindication position calculation method comprising:

causing an imaging section provided in an indicator to acquire an imageof a light emitting section and successively output light-receptioninformation of pixels of the acquired image;

causing a determination section to determine whether or not the pixelsare effective pixels satisfying a given condition based on thelight-reception information; and

causing a calculation section to perform position calculations based onidentification information of the effective pixels in order to obtain anindication position of the indicator when light received by theeffective pixels is included in light emitted from the light-emittingsection,

the calculation section performing the position calculations based onthe identification information of a first effective pixel which is oneof the effective pixels and is primarily determined to satisfy the givencondition; and

the imaging section being provided in the indicator held in a referenceposition when one of the pixels having the light-reception informationoutput primarily is disposed on a lower side of the image and anotherone of the pixels having the light-reception information output last isdisposed on an upper side of the image.

The term “identification information of a pixel” used herein refers toinformation which specifies the position of a pixel in an image. Forexample, the identification information may be address data or a countvalue of a pixel. The term “reference position” used herein refers to apredetermined position (direction or position) of the indicator (i.e.,position at which the starting pixel of the imaging section provided inthe indicator is positioned on the lower side and the end pixel ispositioned on the upper side). The reference position may beappropriately determined depending on the specification of theindication position calculation system and the specification of theindicator. The reference position of the indicator may be an averageposition when using the indicator in a normal state. The term “normalstate” used herein refers to a state determined based on the shape ofthe indicator or a state specified in a manual or the like, for example.

According to the above embodiments, when the user of the system directsthe indicator toward the light-emitting section, the imaging sectionprovided in the indicator acquires an image in a given area includingthe light-emitting section. The determination section determines whetheror not each pixel satisfies a given condition based on thelight-reception information relating to each pixel, and the calculationsection calculates the indication position of the indicator based on thepositions of the effective pixels in the image using the effectivepixels which satisfy a given condition as pixels corresponding to thelight-emitting section.

When pixels corresponding to noise exist, the indication position cannotbe accurately calculated if the position calculations are performedusing the pixels corresponding to noise as pixels corresponding to thelight-emitting section without determining whether or not the effectivepixel is a pixel corresponding to the light-emitting section or a pixelcorresponding to noise.

In an actual situation in which the above indication positioncalculation system is installed, a noise source generally exists at aposition above the light-emitting section. For example, when using aninfrared light source as the light-emitting section, a window throughwhich external light enters or an incandescent lamp may serve as aninfrared light source (i.e., noise source). A window or a lamp generallyexists at a position higher than the light-emitting section. Therefore,pixels corresponding to noise generally occur in an area higher than thelight-emitting section in the image acquired by the imaging section. Onthe other hand, pixels corresponding to noise rarely occur in an arealower than the light-emitting section.

The above embodiments focuses on this situation. Specifically, theimaging section is provided in the indicator so that the starting pixelis disposed on the lower side and the end pixel is disposed on the upperside when the indicator is held in the reference position. The imagingsection successively outputs the light-reception information relating toeach pixel from the starting pixel which corresponds to the lower sideof the image acquired by the imaging section. Specifically, when theindicator is held in the reference position, the imaging sectionsuccessively outputs the light-reception information relating to eachpixel from the pixels positioned on the lower side in which pixelscorresponding to noise rarely occur.

According to the above embodiments, since the first effective pixel ofwhich the light-reception information has been output from the imagingsection and which has been determined to satisfy a given condition isconsidered to be a pixel corresponding to the light-emitting section,the indication position can be accurately calculated using the firsteffective pixel as a pixel corresponding to the light-emitting sectionwithout determining whether the first pixel is a pixel corresponding tothe light-emitting section or a pixel corresponding to noise. Accordingto the above embodiments, since it is unnecessary to determine whetherthe effective pixel which satisfies a given condition is a pixelcorresponding to the light-emitting section or a pixel corresponding tonoise, the indication position can be promptly and accurately calculatedwith a reduced processing load.

(2) In each of the indication position calculation system, the indicatorfor an indication position calculation system, and the indicationposition calculation method,

the calculation section may set a predetermined area of the imageincluding the first effective pixel as a determination area, and performthe position calculations based on the identification information ofpart of the effective pixels included in the determination area.

According to this feature, effective pixels included in thepredetermined determination area can be considered to be pixelscorresponding to the light-emitting section. Therefore, the indicationposition can be more accurately calculated using the identificationinformation relating to the effective pixels included in thepredetermined determination area.

(3) Each of the indication position calculation system, the indicatorfor an indication position calculation system, and the indicationposition calculation method may comprise:

a plurality of the light-emitting sections having a predeterminedpositional relationship with each other,

wherein the calculation section may set a predetermined area of theimage including the first effective pixel as a first determination area,set another predetermined area of the image including a second effectivepixel which has been primarily determined to satisfy the given conditionamong the pixels out of the first determination area as a seconddetermination area, and then perform the position calculations based onthe identification information of the effective pixels within the firstdetermination area and the second determination area.

According to this feature, when the light-emitting section includes afirst light-emitting section and a second light-emitting section, forexample, effective pixels included in the first determination area canbe considered to be pixels corresponding to the first light-emittingsection, and effective pixels included in the second determination areacan be considered to be pixels corresponding to the secondlight-emitting section. When the light-emitting section further includesa third light-emitting section and a fourth light-emitting section, athird determination area and a fourth determination area may be set.Even if the indication position of the indicator is calculated in astate in which a plurality of light-emitting sections are provided, theindication position can be more accurately calculated by using theidentification information relating to the effective pixelscorresponding to each light-emitting section.

(4) In each of the indication position calculation system, the indicatorfor an indication position calculation system, and the indicationposition calculation method,

the determination section may determine whether or not each of thepixels satisfies a first condition and then determine whether or noteach of the pixels satisfies a second condition; and

the calculation section may calculate a representative value of thedetermination area based on the identification information of theeffective pixels and then perform the position calculations based on therepresentative value, while making weight on the identificationinformation of the effective pixels included in the determination areaand satisfying the second condition different from weight on theidentification information of the effective pixels included in thedetermination area but not satisfying the second condition.

According to this feature, weighting on the identification informationrelating to bright effective pixels which are included in thedetermination area in a predetermined range and have a relatively largelight reception can be increased, and weighting on the identificationinformation relating to dark effective pixels which are included in thedetermination area in a predetermined range and have a relatively smalllight reception can be reduced, for example. Therefore, the indicationposition can be more accurately calculated by increasing the degree ofeffects of bright pixels having a relatively large light-receptioninformation as pixels corresponding to a portion near the center of thelight-emitting section and reducing the degree of effects of dark pixelshaving a relatively small light-reception information as pixelscorresponding to the peripheral portion of the light-emitting sectionwhen calculating the representative value of the determination area, forexample.

(5) In each of the indication position calculation system, the indicatorfor an indication position calculation system, and the indicationposition calculation method,

the light-emitting section may emit light in a predetermined wavelengthband; and

the imaging section may have a light reception sensitivity for lightincluding the predetermined wavelength band.

According to this feature, reception of light in another wavelength bandcan be prevented by causing the wavelength band of light emitted fromthe light-emitting section to coincide with the light receptionsensitivity of the imaging section.

(6) Each of the indication position calculation system, the indicatorfor an indication position calculation system, and the indicationposition calculation method may further comprise:

a shielding section provided in the light-emitting section and shieldingpart of light from the light-emitting section emitted downward in apredetermined degrees of angle or less from the horizontal.

According to this feature, even if a reflecting surface which reflectslight from the light-emitting section to produce noise exists at aposition lower than the light-emitting section (e.g., when a glass tableis provided between the light-emitting section and the imaging section(indicator)), reflected light can be prevented from entering the imagingsection from the light-emitting section.

(7) In each of the indication position calculation system, the indicatorfor an indication position calculation system, and the indicationposition calculation method,

the shielding section may be disposed at a position enabling theshielding section to shield part of the light from the light-emittingsection emitted downward from the horizontal so that no reflected lightfrom lower space enters the imaging section when the light-emittingsection and the imaging section have a given reference positionalrelationship.

According to this feature, reflected light can be prevented fromentering the imaging section from the light-emitting section when thelight-emitting section and the imaging section have the referencepositional relationship. Accordingly, reflected light can be reliablyprevented from entering the imaging section from the light-emittingsection when the indication position calculation system is in a basicstate depending on the application.

(8) In each of the indication position calculation system, the indicatorfor an indication position calculation system, and the indicationposition calculation method,

the light-emitting section may be directed in a direction enabling toprevent light from the light-emitting section from being emitteddownward from the horizontal so that no reflected light from lower spaceenters the imaging section when the light-emitting section and theimaging section have a given reference positional relationship.

According to this feature, reflected light can be prevented fromentering the imaging section from the light-emitting section when thelight-emitting section and the imaging section have the referencepositional relationship by adjusting the direction of the light-emittingsection without providing the shielding section. Accordingly, reflectedlight can be reliably prevented from entering the imaging section fromthe light-emitting section when the indication position calculationsystem is in a basic state depending on the application, by adjustingthe direction of the light-emitting section.

(9) Each of the indication position calculation system, the indicatorfor an indication position calculation system, and the indicationposition calculation method may further comprise:

a filter which is provided in the indicator and through which light inthe same wavelength band as light from the light-emitting section isallowed to pass toward the imaging section.

This makes it possible to more accurately calculate the indicationposition by reducing noise due to light in a wavelength band differingfrom that of light emitted from the light-emitting section.

(10) Each of the indication position calculation system, the indicatorfor an indication position calculation system, and the indicationposition calculation method may comprise:

a plurality of the light-emitting sections having a predeterminedpositional relationship with each other,

wherein the calculation section may perform the position calculationsbased on the identification information of the effective pixelscorresponding to each of the light-emitting sections.

This makes it possible to more accurately calculate the indicationposition by calculating the indication position using the positionalrelationship between a plurality of representative values.

(11) According to one embodiment of the invention, there is provided agame system calculating an indication position of an indicator, the gamesystem comprising:

a display section which displays an object;

a light-emitting section which has a given positional relationship withthe display section;

an imaging section which is provided in the indicator, acquires an imageand successively outputs light-reception information of pixels of theacquired image, wherein one of the pixels having the light-receptioninformation output primarily is disposed on a lower side of the imageand another one of the pixels having the light-reception informationoutput last is disposed on an upper side of the image when the indicatoris held in a reference position;

a determination section which determines whether or not the pixels areeffective pixels satisfying a given condition based on thelight-reception information; and

a calculation section which performs position calculations based onidentification information of the effective pixels in order to obtainthe indication position of the indicator when light received by theeffective pixels is included in light emitted from the light-emittingsection,

the calculation section performing the position calculations based onthe identification information of a first effective pixel which is oneof the effective pixels and is primarily determined to satisfy the givencondition.

According to the above embodiment, since it is unnecessary to determinewhether the effective pixel which has been determined to satisfy thegiven condition is a pixel corresponding to the light-emitting sectionor a pixel corresponding to noise, a game system can be provided whichcan promptly and accurately calculate the indication position of theindicator on the display section with a reduced processing load.

These embodiments of the invention will be described below. Note thatthe embodiments described below do not in any way limit the scope of theinvention laid out in the claims herein. In addition, not all of theelements of the embodiments described below should be taken as essentialrequirements of the invention.

1. Outline of System

FIG. 1 is a diagram schematically showing a game system 10 to which anindication position calculation system according to one embodiment ofthe invention is applied. The game system 10 according to thisembodiment includes a display section 12 which displays a game imagesuch as a target object TO on a display screen 11, a light-emitting unit15 which is provided at the top of the display section 12 and includestwo light-emitting sections 13 and 14, each having an infrared lightsource such as an infrared LED, a controller 16 (indicator, shootingdevice, or pointing device) which is held by a player P so that itsposition and direction can be arbitrarily changed and is used toindicate an arbitrary position on the display screen 11, and a gamedevice 17 which performs a game process and the like.

Each of the light-emitting sections 13 and 14 according to thisembodiment has the infrared light source on the front surface. Thelight-emitting sections 13 and 14 are provided on the top surface of thedisplay section 12 at a predetermined interval so that the frontsurfaces face in the same direction as the display screen 11 (i.e.,direction toward the player). Each of the light-emitting sections 13 and14 emits infrared light forward from the light source.

The controller 16 according to this embodiment is formed to imitate theshape of a gun, and includes a barrel GB which is directed toward thedisplay screen 11, a grip GG which extends from the barrel GB and isheld by the player P with the hand, and a trigger GT which can beoperated using the forefinger of the hand holding the grip GG. An imagesensor 18 (light-receiving section or imaging section) such as a CMOSsensors is provided on the end of the barrel GB. The image sensor 18receives infrared light (light in the same wavelength band as lightemitted from the light-emitting sections 13 and 14) which enters theimage sensor 18 along the direction in which the end of the controller16 (barrel GB) is directed, and acquires (images) the infrared light.

In this embodiment, a filter FI which allows only light in a wavelengthband corresponding to infrared light (i.e., light having the samewavelength as light emitted from the light-emitting sections 13 and 14)to pass through is provided on the front side of the image sensor 18(i.e., the end of the controller 16 at a position forward from the imagesensor 18) so that light in a predetermined wavelength band enters theimage sensor 18. An image sensor having a light reception sensitivity ina wavelength band within a predetermined range including infrared light(light having a predetermined wavelength) may be used as the imagesensor 18 without providing the filter FI.

The game system 10 calculates the positional relationship between thelight-emitting sections 13 and 14 and the controller 16 based onposition information relating to the light-emitting sections 13 and 14in an image acquired by the image sensor 18 and reference positioninformation set in advance, and calculates information relating to theindication position of the controller 16 on the display screen 11. Thegame system 10 determines whether or not the indication position of thecontroller 16 when the trigger GT of the controller 16 has been pulledcoincides with the position of the target object TO displayed on thedisplay screen 11, and performs a game process such as an image displaycontrol process or a score calculation process.

FIG. 2 is a diagram showing an example of an image PC1 acquired by theimage sensor 18 when the controller 16 is directed toward the displayscreen 11. The image sensor 18 according to this embodiment includes22,050 (175×126) light-receiving elements (imaging elements) arranged ina matrix on a rectangular surface, and acquires the image PC1. One pixelof the image PC1 corresponds to one light-receiving element. In thisembodiment, the image PC1 is updated every 1/54th of a second dependingon the position and the direction of the controller 16. The game system10 calculates the information relating to the indication position of thecontroller 16 on the display screen 11 using position informationrelating to two infrared light source areas IrA1 and IrA2 (i.e., areasobtained by imaging infrared light from the light-emitting sections 13and 14) in the image PC1. In this embodiment, an origin O (i.e., centerof the image PC1) is considered to be the indication point of thecontroller 16, and information relating to the indication position ofthe controller 16 on the display screen 11 is calculated based on thepositional relationship among the origin O, the infrared light sourceareas IrA1 and IrA2 in the image PC1, and a display screen area DpAwhich is an area corresponding to the display screen 11 in the imagePC1.

In the example shown in FIG. 2, the infrared light source areas IrA1 andIrA2 are formed above the center of the image PC1 to some extent in astate in which a straight line 1 which connects the infrared lightsource areas IrA1 and IrA2 is rotated clockwise by omega degrees withrespect to a reference line L (i.e., X axis of the image sensor 18) ofthe image PC1. In the example shown in FIG. 2, the origin O correspondsto a predetermined position on the lower right of the display screenarea DpA so that the coordinates of the indication position of thecontroller 16 on the display screen 11 can be calculated. The rotationangle of the controller 16 around the indication direction axis withrespect to the display screen 11 can be calculated based on the rotationangle omega of the straight line 1 which connects the infrared lightsource areas IrA1 and IrA2 with respect to the reference line L. Thedistance between the controller 16 and the display screen 11 in theexample shown in FIG. 2 can be calculated based on the ratio of areference distance D between the infrared light source areas IrA1 andIrA2 when the controller 16 is located at a predetermined distance fromthe display screen 11 and a distance d between the infrared light sourceareas IrA1 and IrA2 in the example shown in FIG. 2 by setting thereference distance D in advance.

According to this embodiment, information relating to the indicationposition of the controller 16 on the display screen 11 and the like canbe calculated even if the player P moves his hand while holding thecontroller 16 as shown in FIG. 1 or changes the position and thedirection of the controller 16 due to the movement of the player P.

In the example shown in FIG. 1, the game device 17 and the controller 16are connected via a cable. Note that information may be transmitted andreceived between the game device 17 and the controller 16 via wirelesscommunication. The light-emitting sections 13 and 14 need not benecessarily provided at the top of the display section 12. Thelight-emitting sections 13 and 14 may be provided at an arbitraryposition (e.g., bottom or side) of the display section 12. Specifically,the light-emitting sections 13 and 14 may be provided to have a givenpositional relationship with the display section 12 within a range inwhich the image sensor 18 can receive light when the controller 16 isdirected toward the display screen 11.

2. Configuration of Image Sensor

The details of the configuration of the image sensor 18 according tothis embodiment are as follows. FIG. 3 provides a side view of thecontroller 16 including the image sensor 18 and an enlarged front viewof the image sensor 18. FIG. 3 is a view illustrative the installationstate of the image sensor 18 in the controller 16. As shown in FIG. 3,the image sensor 18 according to this embodiment is provided in thecontroller 16 so that its light-receiving surface SF perpendicularlyintersects an indication direction BD of the barrel GB. The image sensor18 is provided in the controller 16 so that the X axis (reference lineL) of the image sensor 18 perpendicularly intersects an installationdirection GD of the grip GG.

Therefore, when the player P holds the controller 16 so that theinstallation direction GD of the grip GG faces perpendicularly downward,the indication direction BD and the X axis (reference line L) of theimage sensor 18 become horizontal. In this embodiment, a state in whichthe installation direction GD of the grip GG faces perpendicularlydownward is referred to as a reference position of the controller 16.Specifically, the term “reference position of the controller 16” refersto an average position (direction or use state) of the controller 16when the player P holds the controller 16 as if to hold an actual gun.

In the image sensor 18, each of the 22,050 (175×126) light-receivingelements arranged on the rectangular surface SF receives infrared lightwhich enters along the direction in which the end of the controller 16is directed, and successively outputs light-reception informationrelating to each pixel. The controller 16 then determines whether or notthe light-reception information relating to each pixel is larger than athreshold value set corresponding to the quantity of light emitted fromthe light-emitting sections 13 and 14 (i.e., whether or not each pixelis an effective pixel which satisfies a given condition) to determineswhether or not each pixel is a pixel corresponding to the infraredlight. However, a pixel corresponding to infrared light may be a pixelcorresponding to an infrared light source other than the light-emittingsections 13 and 14 (i.e., light source which emits light in the samewavelength band as light emitted from the light that light-emittingsections 13 and 14) instead of a pixel corresponding to thelight-emitting sections 13 and 14.

FIG. 4A is a diagram showing a state around the light-emitting sections13 and 14 viewed from the front side of the display screen 11. Whenforming the game system 10 in a room or the like using a consumer gamedevice as the game device 17 according to this embodiment and using atelevision monitor as the display section 12, an infrared light sourceother than the light-emitting sections 13 and 14 may exist. As shown inFIG. 4A, a window WD through which external light enters, anincandescent lamp WH, and the like serve as infrared light sources. Whenthe image sensor 18 receives infrared light which enters through thewindow WD, light emitted from the incandescent lamp WH, and the like,the received infrared light serves as noise so that an accurateindication position may not be calculated.

FIG. 4B shows an image PC2 acquired by the image sensor 18 in a stateshown in FIG. 4A when the controller 16 is held in the referenceposition toward the display screen 11. As shown in FIG. 4A, the windowWD, the incandescent lamp WH, and the like are generally positionedabove the light-emitting sections 13 and 14 disposed at the top of thedisplay screen 11 in a real space. In an image PC2 acquired by the imagesensor 18, as shown in FIG. 4B, pixels corresponding to a noise area NA1due to the window WD and a noise area NA2 due to the incandescent lampWH generally occur in an area UA obtained by imaging a portion above thelight-emitting sections 13 and 14.

A related-art indication position calculation system successivelyoutputs the light-reception information relating to each pixel whilescanning each row from the upper row to the lower row, starting from theuppermost-leftmost pixel (starting pixel) toward the lowermost-rightmostpixel (end pixel) in the image PC2 shown in FIG. 4B, and determineswhether or not each pixel is a pixel corresponding to the light source.Specifically, in a related-art indication position calculation system,the image sensor 18 is provided in the controller 16 so that thestarting pixel is disposed on the upper side and the end pixel isdisposed on the lower side when the controller 16 is held in thereference position. Therefore, a related-art indication positioncalculation system successively outputs the light-reception informationrelating to each pixel from upper pixels in which pixels correspondingto noise tend to occur. Accordingly, pixels corresponding to the lightsource include not only pixels corresponding to the light-emittingsections 13 and 14, but also pixels corresponding to the noise areas NA1and NA2. Therefore, a related-art indication position calculation systemmust distinguish pixels corresponding to the light-emitting sections 13and 14 from pixels corresponding to noise.

On the other hand, pixels corresponding to noise rarely occur in an areaDA obtained by imaging a portion below the light-emitting sections 13and 14, as shown in FIG. 4B. In this embodiment, the image sensor 18 isprovided in the controller 16 so that a starting pixel SP is disposed onthe lower side and an end pixel EP is disposed on the upper side whenthe controller 16 is held in the reference position, taking such asituation into consideration. The image sensor 18 horizontally scanspixels in the leftward direction from the lowermost-rightmost pixel inthe acquired image PC2 as the starting pixel SP. When the pixels in thelowermost row have been completely scanned, the image sensor 18horizontally scans pixels in the next (upper) row in the leftwarddirection from the rightmost pixel. The image sensor 18 successivelyoutputs the light-reception information relating to each pixel whilescanning pixels in each row from the lower row to the upper row untilthe uppermost-leftmost end pixel EP is reached. Specifically, when thecontroller 16 is held in the reference position, the image sensor 18successively outputs the light-reception information relating to eachpixel from pixels on the lower side in which pixels corresponding tonoise rarely occur.

According to this embodiment, a first effective pixel FP of which thelight-reception information has been output from the image sensor 18 andwhich has been determined to satisfy a given condition is a pixelcorresponding to the light-emitting section 13 or 14 when the controller16 is held in the reference position. Therefore, the indication positioncan be accurately calculated using the first effective pixel FP as apixel corresponding to the light-emitting section 13 or 14 withoutdetermining whether the pixel corresponding to the light source is apixel corresponding to the light-emitting section 13 or 14 or a pixelcorresponding to noise. According to this embodiment, since it isunnecessary to determine whether the effective pixel which has beendetermined to satisfy a given condition is a pixel corresponding to thelight-emitting section 13 or 14 or a pixel corresponding to noise, theindication position can be promptly and accurately calculated with areduced processing load.

3. Circuit Configuration

FIG. 5 is a functional block diagram showing an indication positiondetection section provided in the controller 16 according to thisembodiment. The indication position detection section includes the imagesensor 18, an ASIC 200, an MCU 300, and a USB 400.

The image sensor 18 is initialized when the image sensor 18 has receivedan initialization signal from the MCU 300. The image sensor 18 acquiresthe light-reception information in pixel units by receiving infraredlight which enters along a direction in which the end of the controller16 is directed to acquire an image along the direction in which the endof the controller 16 is directed. In this embodiment, thelight-reception information (quantity of received light) of each pixelis acquired using a two-digit hexadecimal number in the range from 00 toFF. A starting pixel is set on one end of the acquired image, and an endpixel is set on the other end. The image sensor 18 successively outputsthe light-reception information relating to each pixel from the startingpixel to the end pixel to the ASIC 200.

The image sensor 18 outputs a pixel clock signal and a verticalsynchronization signal to a control section 220 of the ASIC 200, andoutputs the pixel clock signal to a pixel counter 230. This allows thecontrol section 220 and the pixel counter 230 to synchronize with theoutput timing of the light-reception information relating to each pixelfrom the image sensor 18.

The ASIC 200 includes a determination section 210, the control section220, and the pixel counter 230.

The determination section 210 determines whether or not each pixelsatisfies a given condition based on the light-reception informationrelating to each pixel successively output from the image sensor 18.Specifically, the determination section 210 determines that a firstcondition is satisfied when the light-reception information relating toeach pixel is 80 (two-digit hexadecimal number) or more. Thedetermination section 210 determines that a pixel of which thelight-reception information is 80 or more to be a pixel corresponding tothe infrared light source.

In this embodiment, the determination section 210 determines whether ornot each pixel satisfies the first condition, and determines whether ornot an effective pixel which satisfies the first condition satisfies asecond condition. Specifically, a pixel group of pixels corresponding tothe light source is bright at the center and becomes darker as thedistance from the center increases due to a decrease in luminance. Inthis embodiment, the determination section 210 determines that thesecond condition is satisfied when the light-reception informationrelating to an effective pixel is F0 or more. The determination section210 determines that a pixel of which the light-reception information is80 to EF to be a dark pixel corresponding to the peripheral portion ofthe infrared light source, and determines that a pixel of which thelight-reception information is F0 to FF to be a bright pixelcorresponding to the center portion of the infrared light source.

The determination section 210 outputs an enable signal to the controlsection 220 while determining whether or not the light-receptioninformation relating to each pixel successively output from the imagesensor 18 satisfies the first condition. When the light-receptioninformation relating to each pixel satisfies the second condition,determination section 210 outputs a bright signal which indicates thepixel is bright to a pixel FIFO 340 of the MCU 300.

The control section 220 allows a 15-bit count value output from thepixel counter 230 to be written into the pixel FIFO 340 when the controlsection 220 receives the enable signal from the determination section210. The pixel counter 230 is reset upon reception of the verticalsynchronization signal output from the image sensor 18 from the controlsection 220, and outputs the 15-bit count value from the starting pixel(0) to the end pixel (22,050) of the image sensor 18 in synchronizationwith the output of the light-reception information relating to eachpixel. In this embodiment, the count value of an effective pixel ofwhich the light-reception information has been determined to satisfy thefirst condition is written into the pixel FIFO 340.

In this case, the pixel counter 230 writes 16-bit data into the pixelFIFO 340 by adding 0 as the most significant bit of the 15-bit countvalue when the bright signal is received from the determination section210 and adding 1 as the most significant bit of the 15-bit count valuewhen the bright signal is not received from the determination section210. Specifically, the count value of an effective pixel of which thelight-reception information has been determined to satisfy the firstcondition and the data which indicates whether or not the effectivepixel satisfies the second condition (16 bits in total) are stored inthe pixel FIFO 340.

The MCU 300 includes the pixel FIFO 340, a light source positioncalculation section 350, and an indication position calculation section360.

The pixel FIFO 340 stores 128 pieces of 16-bit data relating to theeffective pixel based on the data output from the ASIC 200. The pixelFIFO 340 successively outputs the 16-bit data relating to each effectivepixel to the light source position calculation section 350 in a first-infirst-out manner.

The light source position calculation section 350 sets a firstdetermination area in a predetermined range including a first effectivepixel based on first data stored in the pixel FIFO 340 after the imagesensor 18 has been initialized (i.e., the count value of the firsteffective pixel which has been determined to satisfy the firstcondition). The light source position calculation section 350 sets asecond determination area in a predetermined range including a secondeffective pixel based on the count value of the second effective pixelwhich is a pixel in the area other than the first determination area andis a first pixel which has been determined to satisfy the firstcondition). The light source position calculation section 350 performsposition calculations based on the count values (identificationinformation) of effective pixels which satisfy the first condition andare included in the first determination area and the count values ofeffective pixels which satisfy the first condition and are included inthe second determination area.

FIG. 6 shows part of an enlarged image acquired by the image sensor 18.FIG. 6 is a view illustrative of calculations of a representative valueof the determination area. In FIG. 6, a white square indicates aneffective pixel which satisfies the first condition and the secondcondition, a gray square indicates an effective pixel which satisfiesthe first condition but does not satisfy the second condition, and ablack area indicates ineffective pixels which do not satisfy the firstcondition and the second condition. As shown in FIG. 6, the image sensor18 horizontally and sequentially scans pixels from the lower right pixeland outputs the light-reception information relating to each pixel. Whenthe determination section 210 determines whether or not each pixelsatisfies the first condition, the determination section 210 determinesthat a pixel P1 is a first effective pixel which satisfies the firstcondition. When the 16-bit data relating to the first effective pixel P1is input to the light source position calculation section 350 from thepixel FIFO 340, the light source position calculation section 350 sets afirst determination area JA1 in a circular region in a predeterminedrange including the first effective pixel, as shown in FIG. 6.Specifically, the light source position calculation section 350 sets thefirst determination area JA1 in a range in which it is estimated thatother effective pixels corresponding to the light-emitting section 13 or14 exist when the first effective pixel is a pixel corresponding to thelight-emitting section 13 or 14.

The light source position calculation section 350 determines whether ornot each effective pixel is included in the first determination area JA1based on the count value of each effective pixel sequentially input fromthe pixel FIFO 340. The light source position calculation section 350calculates a representative value (center-of-gravity coordinates) of thefirst determination area based on the count value of each effectivepixel included in the first determination area JA1. In this embodiment,the light source position calculation section 350 transforms the countvalue of each effective pixel into a coordinate value of each pixel inan image PC acquired by the image sensor 18, and then calculates thecenter-of-gravity coordinates of the first determination area JA1.

Specifically, the light source position calculation section 350calculates a remainder when dividing the count value (one of 0 to22,050) by 175 which is the number of pixels on the X axis of the imagesensor 18 to calculate the X coordinate of the pixel in the image fromthe count value, and calculates a quotient when dividing the count valueby 175 to calculate the Y coordinate of the pixel in the image from thecount value. For example, the light source position calculation section350 calculates a coordinate value (0, 0) from the count value 0 of thestarting pixel as indicated by X=0 mod 175=0 and Y=0/175=0. The lightsource position calculation section 350 calculates a coordinate value(47, 82) from the count value 14397 as indicated by X=14397 mod 175=47and Y=14397/175=82.

The light source position calculation section 350 divides the sum of theX coordinate components of the effective pixels included in the firstdetermination area JA1 by the number of the effective pixels included inthe first determination area JA1 to calculate the X coordinate componentof the center-of-gravity coordinates of the first determination areaJA1. Likewise, the light source position calculation section 350 dividesthe sum of the Y coordinate components of the effective pixels includedin the first determination area JA1 by the number of the effectivepixels included in the first determination area JA1 to calculate the Ycoordinate component of the center-of-gravity coordinates of the firstdetermination area JA1. In this embodiment, the light source positioncalculation section 350 calculates the center-of-gravity coordinates ofthe first determination area JA1 based on the coordinate component valueof each effective pixel while changing weighting on the coordinatecomponent value of each effective pixel between an effective pixel whichis included in the first determination area JA1 and satisfies the secondcondition (bright pixel) and an effective pixel which is included in thefirst determination area JA1 and does not satisfy the second condition(dark pixel).

Specifically, the light source position calculation section 350 performsthe above calculations while doubling the coordinate component value andthe number of bright pixels. In the example shown in FIG. 6, pixels P7and P13 of which the X coordinate component value is 45 are brightpixels. Therefore, the coordinate component values 45×2 of the pixels P7and P13 are doubled and added to the coordinate component value. Thenumber of bright pixels (2) is also doubled and added to the number ofpixels. Since a pixel P19 is a dark pixel, the coordinate componentvalue 45 of the pixel P19 is directly added to the coordinate componentvalue, and the number of bright pixels (1) is directly added to thenumber of pixels. The pixels having other X coordinate component valuesare similarly calculated. Therefore, the X component X1 of thecenter-of-gravity coordinates of the first determination area JA1 in theexample shown in FIG. 6 is calculated as follows.

$\begin{matrix}{{X1} = \left\lbrack {{2*\left( {{45*2} + {46*3} + {47*6} + {48*6} + {49*5} + {50*2}} \right)} +} \right.} \\{\left. \left( {45 + {46*2} + 47 + 50} \right) \right\rbrack/\left\lbrack {{2*\left( {2 + 3 + 6 + 6 + 5 + 2} \right)} +} \right.} \\\left. \left( {1 + 2 + 1 + 1} \right) \right\rbrack \\{= {\left( {2286 + 234} \right)/\left( {48 + 5} \right)}} \\{= {2520/53}} \\{= 47.547}\end{matrix}$

Likewise, the Y component Y1 of the center-of-gravity coordinates of thefirst determination area JA1 is calculated as follows.

$\begin{matrix}{{Y1} = \left\lbrack {{2*\left( {81 + {82*3} + {83*5} + {84*6} + {85*5} + {86*3} + 87} \right)} +} \right.} \\{\left. \left( {81 + 82 + 83 + 85 + 86} \right) \right\rbrack/\left\lbrack {{2*\left( {1 + 3 + 5 + 6 + 5 + 3 + 1} \right)} +} \right.} \\\left. \left( {1 + 1 + 1 + 1 + 1} \right) \right\rbrack \\{= {\left( {4032 + 417} \right)/\left( {48 + 5} \right)}} \\{= {2520/53}} \\{= 84.962}\end{matrix}$

Specifically, the center-of-gravity coordinates (X1, Y1) of the firstdetermination area JA1 in the example shown in FIG. 6 are calculated tobe (47.547, 84.962).

The light source position calculation section 350 sets a seconddetermination area JA2 in a predetermined range including a secondeffective pixel which is included in an area other than the firstdetermination area JA1 and is a first pixel which has been determined tosatisfy the first condition, and calculates the center-of-gravitycoordinates (X2, Y2) of the second determination area JA2 in the samemanner as the first determination area JA1. The light source positioncalculation section 350 outputs the center-of-gravity coordinates (X1,Y1) of the first determination area JA1 and the center-of-gravitycoordinates (X2, Y2) of the second determination area JA2 to theindication position calculation section 360.

The indication position calculation section 360 calculates theindication position of the controller 16 on the display screen 11 basedon the center-of-gravity coordinates (X1, Y1) of the first determinationarea JA1 and the center-of-gravity coordinates (X2, Y2) of the seconddetermination area JA2. Specifically, the indication positioncalculation section 360 calculates the positional relationship betweenthe light-emitting sections 13 and 14 and the controller 16 using thecenter-of-gravity coordinates (X1, Y1) of the first determination areaJA1 or the center-of-gravity coordinates (X2, Y2) of the seconddetermination area JA2 relatively positioned on the left of the image PCas the center coordinates of the light-emitting section 13 disposed onthe upper left portion of the display section 12 and thecenter-of-gravity coordinates (X1, Y1) or the center-of-gravitycoordinates (X2, Y2) relatively positioned on the right of the image PCas the center coordinates of the light-emitting section 14 disposed onthe upper right portion of the display section 12, and calculates theindication position of the controller 16 on the display screen 11. Theindication position calculation section 360 outputs the calculatedindication position to the USB 400.

The USB 400 includes a USB interface 410 and a key function section 420.

The USB interface 410 outputs the indication position data input fromthe MCU 300 to the game device 17. The key function section 420 outputsan operation signal based on operation of the trigger and otheroperation keys of the controller 16. The game device 17 identifies theindication position data relating to the controller 16 at a timing atwhich the trigger operation signal is input to be an impact position ofa virtual bullet on a game screen (display screen 11), and performs gamecalculations such as determining whether or not the target has been hit.

4. Flow of Position Calculation Process

The flow of a position calculation process of the controller 16 isdescribed below using a flowchart. FIG. 7 is a flowchart showing anexample of an outline of the position calculation process according tothis embodiment. As shown in FIG. 7, the determination section 210determines whether or not each pixel satisfies a given condition basedon the light-reception information relating to each pixel output fromthe image sensor 18 (step S10). The light source position calculationsection 350 calculates the center-of-gravity positions of twodetermination areas corresponding to the two light sources based on theidentification information relating to the first effective pixel and thesecond effective pixel (step S12). The indication position calculationsection 360 calculates the indication position of the controller 16based on the center-of-gravity positions of the two determination areas(step S14). The indication position calculation section 360 outputs theindication position of the controller 16 to the game device 17 (stepS16). In this embodiment, the process in the steps S10 to S16 isrepeated every 1/54th of a second.

FIG. 8 is a flowchart showing an example of the details of the pixeldetermination process in the step S10 shown in FIG. 7. As shown in FIG.8, the determination section 210 acquires the light-receptioninformation from the image sensor 18 in pixel units (step S100), anddetermines whether or not the light-reception information is equal to orlarger than a first threshold value (i.e., satisfies the firstcondition) (step S102). When the determination section 210 hasdetermined that the light-reception information is not equal to orlarger than the first threshold value (N in step S102), thedetermination section 210 acquires the light-reception informationrelating to another pixel (step S100). When the determination section210 has determined that the light-reception information is equal to orlarger than the first threshold value (Y in step S102), thedetermination section 210 determines whether or not the light-receptioninformation is equal to or larger than a second threshold value (i.e.,satisfies the second condition) (step S104). When the determinationsection 210 has determined that the light-reception information is equalto or larger than the second threshold value (Y in step S104), thedetermination section 210 sets the most significant bit of the 16-bitdata at 0 as the attribute bit (step S106). When the determinationsection 210 has determined that the light-reception information is notequal to or larger than the second threshold value (N in step S104), thedetermination section 210 sets the most significant bit of the 16-bitdata at 1 as the attribute bit (step S108). The determination section210 stores the 16-bit data in which the most significant bit is theattribute bit and the lower-order 15 bits are the count value of thepixel in the pixel FIFO 340 (step S110). In this embodiment, the processin the steps S100 to S110 is repeatedly performed on each pixel of theimage sensor 18 in synchronization with the pixel clock signal outputfrom the image sensor 18.

FIG. 9 is a flowchart showing an example of the details of the lightsource position calculation process in the step S12 shown in FIG. 7. Asshown in FIG. 9, the light source position calculation section 350acquires the 16-bit data relating to the first effective pixel from thepixel FIFO 340, and separates the lower-order 15-bit count value intothe X component value and the Y component value (step S200). The lightsource position calculation section 350 determines whether or not thefirst determination area has been set (step S202). When the light sourceposition calculation section 350 has determined that the firstdetermination area has not been set (N in step S202), the light sourceposition calculation section 350 determines the pixel to be the firsteffective pixel, and sets the first determination area in an area in apredetermined range including the first effective pixel (step S204).

The light source position calculation section 350 determines whether ornot the most significant bit of the 16-bit data is 0 (step S206). Whenthe light source position calculation section 350 has determined thatthe most significant bit is 0 (i.e., bright pixel) (Y in step S206), thelight source position calculation section 350 doubles the X componentvalue, the Y component value, and the number of pixels (step S208), andadds the X component value to a register RX1, the Y component value to aregister RY1, and the number of pixels to a register RC1 (step S210).When the light source position calculation section 350 has determinedthat the most significant bit is 1 (i.e., dark pixel) (N in step S206),the light source position calculation section 350 adds the X componentvalue to the register RX1, the Y component value to the register RY1,and the number of pixels to the register RC1 without doubling the Xcomponent value, the Y component value, and the number of pixels (stepS210).

The light source position calculation section 350 determines whether ornot the process from the step S200 has been performed on all effectivepixels included in the pixels 0 to 22,050 (pixels of one frame) of theimage sensor 18 (step S212). When the light source position calculationsection 350 has determined that the process has been performed on alleffective pixels (N in step S212), the light source position calculationsection 350 returns to the step S200, and acquires the 16-bit datarelating to the next pixel from the pixel FIFO 340. The light sourceposition calculation section 350 repeats the process in the steps S200to S212.

With regard to the next effective pixel, the light source positioncalculation section 350 determines that the first determination area hasbeen set in the step S202 (Y in step S202), and determines whether ornot the effective pixel is positioned in the first determination areabased on the coordinate value of the effective pixel (step S214). Whenthe light source position calculation section 350 has determined thatthe effective pixel is positioned in the first determination area (Y instep S214), the light source position calculation section 350 performsthe process in the steps S206 to S212. When the light source positioncalculation section 350 has determined that the effective pixel is notpositioned in the first determination area (N in step S214), the lightsource position calculation section 350 determines whether or not thesecond determination area has been set (step S216).

When the light source position calculation section 350 has determinedthat the second determination area has not been set (N in step S216),the light source position calculation section 350 determines theeffective pixel to be the second effective pixel, and sets the seconddetermination area in an area in a predetermined range including thesecond effective pixel (step S218). In steps S220 to S224, the lightsource position calculation section 350 performs a process similar tothe process in the steps S206 to S210 performed on the effective pixelin the first determination area, and adds the X component value to aregister RX2, the Y component value to a register RY2, and the number ofpixels to a register RC2 (step S224).

When the light source position calculation section 350 has determinedthat the second determination area has been set in the step S216 (Y instep S216), the light source position calculation section 350 determineswhether or not the effective pixel is positioned in the seconddetermination area based on the coordinate value of the effective pixel(step S226). When the light source position calculation section 350 hasdetermined that the effective pixel is positioned in the seconddetermination area (Y in step S226), the light source positioncalculation section 350 performs the process in the steps S220 to S224.When the light source position calculation section 350 has determinedthat the effective pixel is not positioned in the second determinationarea (N in step S226), the light source position calculation section 350determines whether or not all effective pixels have been processedwithout adding a value to the register (step S212).

When the light source position calculation section 350 has determinedthat all effective pixels have been processed (Y in step S212), thelight source position calculation section 350 determines whether or notdata relating to the two determination areas has been acquired (stepS228). When the light source position calculation section 350 hasdetermined that data relating to the two determination areas has beenacquired (Y in step S228), the light source position calculation section350 divides the sum of the values stored in the register RX1 by the sumof the values stored in the register RC1 to calculate the X component X1of the center-of-gravity coordinated of the first determination area,divides the sum of the values stored in the register RY1 by the sum ofthe values stored in the register RC1 to calculate the Y component Y1 ofthe center-of-gravity coordinated of the first determination area,divides the sum of the values stored in the register RX2 by the sum ofthe values stored in the register RC2 to calculate the X component X2 ofthe center-of-gravity coordinated of the second determination area, anddivides the sum of the values stored in the register RY2 by the sum ofthe values stored in the register RC2 to calculate the Y component Y2 ofthe center-of-gravity coordinated of the second determination area. Thelight source position calculation section 350 outputs thecenter-of-gravity coordinates (X1, Y1) of the first determination areaand the center-of-gravity coordinates (X2, Y2) of the seconddetermination area to the indication position calculation section 360(step S232).

When the light source position calculation section 350 has determinedthat data relating to the two determination areas has not been acquired(i.e., only data relating to the first determination area has beenacquired) (N in step S228), the light source position calculationsection 350 performs an out-of-range setting which indicates that thecontroller 16 is directed in an area outside the detection range (stepS234), and outputs the setting information to the indication positioncalculation section 360 (step S236).

When the light source position calculation section 350 has output thedata to the indication position calculation section 360, the lightsource position calculation section 350 initializes each register andthe determination areas (step S238). The process in the steps S200 toS238 is repeated each time the image sensor 18 is initialized, and afirst effective pixel of the next frame is output from the pixel FIFO340.

5. Configuration of Light-Emitting Section

The details of the configuration of the light-emitting section accordingto this embodiment are described below.

5-1. Noise Prevention by Shielding Section

FIG. 10A is a side view showing a state in which the controller 16 isdirected toward the display screen 11. In this embodiment, each of thelight-emitting sections 13 and 14 includes a light source 22 which emitsinfrared light that has a certain directivity and travels in a directionwithin a given range so that the image sensor 18 can receive theinfrared light from the light-emitting sections 13 and 14 when thecontroller 16 and the light-emitting sections 13 and 14 have apositional relationship within a predetermined range. Specifically, eachof the light-emitting sections 13 and 14 causes the light source 22 toemit infrared light so that the infrared light travels in a traveldirection within a given range with respect to a center direction CDwhich is the direction of the light source 22. The center direction ofthe light source 22 may be a center luminous intensity direction(maximum luminous intensity direction) of the light source 22, forexample.

As shown in FIG. 10A, when forming the game system 10 in a room or thelike, an object (e.g., mirror or glass table) which reflects theinfrared light from the light source 22 may exist between the lightsource 22 and the image sensor 18. Since the light from the light source22 travels in a direction within a given range, reflected light RLhaving the same wavelength and intensity as direct light DL from thelight source 22 may occur at a position differing from the position ofthe light source 22 (e.g., reflecting surface such as mirror or glasstable). If the image sensor 18 receives the reflected light RL, anaccurate indication position cannot be calculated due to the reflectedlight RL as noise.

FIG. 11A shows an image PC3 acquired by the image sensor 18 in the stateshown in FIG. 10A. In the state shown in FIG. 10A, since the imagesensor 18 receives the direct light DL from the light sources 22 and thereflected light RL, noise areas NA3 and NA4 corresponding to thereflected light RL occur under the infrared light source areas IrA1 andIrA2 corresponding to the light sources 22, as shown in FIG. 11A.

In this embodiment, as shown in FIG. 11B, the reflected light RL whichoccurs below the light-emitting sections 13 and 14 is prevented byproviding a shielding section 24 which shields light that travelsdownward from the light source 22 (light-emitting sections 13 and 14).Specifically, the shielding section 24 is provided at a position atwhich the direct light DL from the light source 22 is prevented fromtraveling in the direction in which the reflected light RL that entersthe image sensor 18 occurs when the light source 22 (light-emittingsections 13 and 14) and the image sensor 18 (controller 16) have a givenreference positional relationship. Therefore, the image sensor 18receives the direct light DL from the light source 22 and does notreceive the reflected light RL when the light source 22 (light-emittingsections 13 and 14) and the image sensor 18 (controller 16) have a givenreference positional relationship.

In this embodiment, the light source 22 and the image sensor 18 have thereference positional relationship when the controller 16 is held in theabove-mentioned reference position, is located at a reference positionaway from the light-emitting sections 13 and 14 by four meters, and ispositioned in a reference direction in which the controller 16 isdirected toward the light source 22. The position, direction, size,shape, and the like of the shielding section 24 are determined so thatthe reflected light RL does not enter within the angle of view theta(Light-reception range) of the image sensor 18 when the light source 22and the image sensor 18 have the reference positional relationship.

In this embodiment, the position, direction, size, shape, and the likeof the shielding section 24 are determined provided that a position atthe maximum distance from the light source 22 at which the image sensor18 can obtain a quantity of light (luminous intensity or luminous flux)necessary for the game system 10 to calculate an accurate indicationposition from the light source 22 is set to be the reference positionand an average (basic) direction of the controller 16 when the playerplays a game while holding the controller 16 toward the display screen11 is set to be the reference direction. In the example shown in FIG.10B, a plate-shaped shielding section 24 is provided under the lightsource 22 at a position near the light source 22 to protrude forwardfrom the front surface of each of the light-emitting sections 13 and 14.Therefore, light which travels downward from the light source 22 in adirection within a predetermined angle phi can be shielded by theshielding section 24.

FIG. 11B shows light received by the image sensor 18 (i.e., image datastored in image data area PA) in the state shown in FIG. 10B. In thestate shown in FIG. 10B, since the image sensor 18 receives the directlight DL from the light sources 22 but does not receive the reflectedlight RL, the noise areas NA3 and NA4 corresponding to the reflectedlight RL do not occur under the infrared light source areas IrA1 andIrA2 corresponding to the light sources 22, as shown in FIG. 11B.

Therefore, according to this embodiment, the reflected light RL whichenters the image sensor 18 does not occur when the controller 16 isdirected toward the display screen 11 within a game play range in whichthe distance between the light-emitting sections 13 and 14 and thecontroller 16 is four meters or less, as shown in FIG. 10B. Thereflected light RL also occurs in FIG. 10B. However, the reflected lightRL does not enter the image sensor 18 unless the controller 16 ispositioned outside the game play range.

Note that the reference positional relationship is not limited to theabove-mentioned example. Various positional relationships may be set.For example, the reference position may be set depending on theintensity of the light source 22 (i.e., distance at which the quantityof light and the like necessary for calculating an accurate indicationposition are ensured), the luminous intensity distribution curve, andthe beam angle (i.e., diffusion range of predetermined quantity oflight). The reference direction may be set depending on the applicationof the indication position calculation system. Specifically, thereference direction may be appropriately set depending on the basicposition of an operator (player P) who holds an indicator (controller16) with respect to the indication plane (display screen 11). Forexample, when applying the indication position calculation systemaccording to this embodiment to a presentation system, the operator whooperates the indicator is rarely positioned perpendicularly to theindication plane (e.g., screen), but is generally positioned diagonallyin front of the indication plane. The operator generally directs theindicator toward the indication plane (light source) disposed above theoperator. In this case, a direction upward from a position diagonally infront of the indication plane may be set to be the reference direction.

5-2. Details of Shielding Section

FIG. 12 is a perspective view of the light-emitting section 13 (14) ofthe light-emitting unit 15 according to this embodiment. In thisembodiment, the light-emitting section 13 (14) is disposed in a state inwhich a bottom surface 32 of a housing 30 is secured on the top surfaceof the display section 12. The housing 30 has a front surface 34 and aback surface 36. Three LED light sources 22-1 to 22-3 which emitinfrared light from the front surface 34 are provided on the frontsurface 34. In this embodiment, the light sources 22-1 to 22-3 aredisposed to form vertices of an inverted triangle when viewed from thetravel direction of light emitted from the light sources 22-1 to 22-3.Therefore, even if the distance between the light sources 22-1 to 22-3and the image sensor 18 increases, the image sensor 18 can reliablyreceive the infrared light from the light sources 22-1 to 22-3 as lighthaving a predetermined area.

A cover 38 which allows the infrared light from the light sources 22-1to 22-3 to pass through is provided on the front surface 34 of thehousing 30 to protect the light sources 22-1 to 22-3. The shieldingsection 24 which protrudes from the front surface 34 is provided at thelower end of the front surface 34 of the housing 30 (i.e., below thelight sources 22-1 to 22-3). In this embodiment, the shielding section24 is integrally formed with the housing 30. A material which does notallow the infrared light from the light sources 22-1 to 22-3 to passthrough is used for the shielding section 24. Therefore, light emittedfrom the light sources 22-1 to 22-3 downward in a predetermined degreesof angle or less from the horizontal can be shielded by the shieldingsection 24.

FIG. 13 is a side view of the light-emitting section 13 (14) shown inFIG. 12. In this embodiment, an angle alpha formed by a shieldingsurface 40 (i.e., top surface) of the shielding section 24 and the frontsurface 34 of the housing 30 is an acute angle, as shown in FIG. 13.Therefore, a protrusion distance 1 of the shielding section 24 from thefront surface 34 necessary for shielding light which travels in adirection within a predetermined range can be reduced as compared withthe case where the angle alpha is a right angle or a obtuse angle. Inthis embodiment, the angle alpha is set at 70 degrees, and theprotrusion distance 1 is set at 7 mm. According to the example shown inFIG. 13, protrusion of the light-emitting section 13 (14) can beprevented and the size of the light-emitting section 13 (14) can bereduced even if the shielding section 24 is provided.

5-3. Noise Prevention Due to Direction of Light Source

The above description has been given taking an example in which thereflected light as noise is prevented by providing the shielding section24 on the front surface of each of the light-emitting sections 13 and 14to shield light which travels downward from the light sources 22-1 to22-3. Note that the reflected light as noise may be prevented bypreventing light from traveling downward from the light sources 22-1 to22-3 by adjusting the directions of the light sources 22-1 to 22-3disposed in the light-emitting sections 13 and 14. Specifically, thecenter direction CD of the light sources 22-1 to 22-3 may be adjusted toa direction in which the direct light DL from the light source 22 isprevented from traveling in the direction in which the reflected lightRL that enters the image sensor 18 occurs when the light source 22(light-emitting sections 13 and 14) and the image sensor 18 (controller16) have a given reference position relationship.

FIG. 14 shows an example of the light-emitting section 13 (14) of whichthe light sources 22-1 to 22-3 are disposed so that the center directionCD of the light sources 22-1 to 22-3 faces upward by beta degrees withrespect to a horizontal direction (direction normal to the displayscreen 11 of the display section 12) HD when the light-emitting section13 (14) is disposed in a state in which the bottom surface 32 of thehousing 30 is secured on the top surface of the display section 12. Inthe example shown in FIG. 14, direct light from the light source 22 isprevented from traveling in a direction in which reflected light entersthe image sensor 18 by adjusting the center direction CD of the lightsources 22-1 to 22-3 upward by beta degrees. Therefore, occurrence ofreflected light which serves as noise under the light sources 22-1 to22-3 can be prevented in the same manner as in the example shown in FIG.13.

6. Light-Reception Range of Image Sensor

A Light-reception range in which the image sensor 18 can receive lightfrom the light sources 22-1 to 22-3 in the game system 10 according tothis embodiment is described below. In this embodiment, three lightsources 22-1 to 22-3 which differ in center direction are disposed inthe light-emitting section 13 (14) so that the image sensor 18 canreceive infrared light from the light-emitting sections 13 and 14 whenthe controller 16 and the light-emitting sections 13 and 14 have apositional relationship within a specific range.

FIG. 15A is a front view of the light-emitting section 13 (14) accordingto this embodiment, and FIG. 15B is a top view of the light-emittingsection 13 (14). As shown in FIG. 15A, the three light sources 22-1 to22-3 of the light-emitting section 13 (14) according to this embodimentare disposed to form vertices of an inverted triangle. As shown in FIG.15B, the lowermost first light source 22-1 is disposed so that a centerdirection CD1 of the light source 22-1 coincides with a first directionD1 which is a reference direction SD of the light-emitting section 13(14).

In the light-emitting section 13 (14) according to this embodiment, thereference direction SD is the front direction of the display screen 11which is the basic direction of the player P who holds the controller16. Specifically, a direction parallel to the direction normal to thedisplay screen 11 of the display section 12 when the light-emittingsection 13 (14) is disposed in a state in which the bottom surface 32 ofthe housing 30 is secured on the top surface of the display section 12is set to be the reference direction SD. In this embodiment, apredetermined range around the front direction of the display screen 11(i.e., basic direction of the player P) in which light travels from thefirst light source 22-1 may be set to be the Light-reception range ofthe image sensor 18.

Since the image sensor 18 successively outputs the light-receptioninformation relating to each pixel while scanning the pixels of theacquired image PC from the lower row to the upper row, the image sensor18 outputs the light-reception information relating to a pixel in theimage PC corresponding to the lowermost first light source 22-1 prior topixels corresponding to the light sources 22-2 and 22-3. Therefore, apixel corresponding to the first light source 22-1 is determined to be afirst effective pixel which satisfies a given condition. In thisembodiment, the maximum luminous intensity direction of the first lightsource 22-1 corresponding to the first effective pixel is set to be thefront direction of the display screen 11 (basic direction of the playerP) by causing the center direction CD1 of the first light source 22-1 tocoincide with the front direction of the display screen 11. According tothis embodiment, when the player P directs the controller 16 toward thedisplay screen 11 along the front direction of the display screen 11, afirst effective pixel can be reliably determined by light which travelsfrom the lowermost first light source 22-1.

As shown in FIG. 15B, the second light source 22-2 positioned on theleft when viewed from the front surface (light travel direction) isdisposed so that a center direction CD2 of the light source 22-2coincides with a second direction D2 which differs from the referencedirection SD by an angle gamma of 90 degrees or less. In thisembodiment, the second light source 22-2 is disposed so that the centerdirection CD2 differs from the reference direction SD by 60 degreestoward the left when viewed from the front surface. Therefore, the imagesensor 18 can receive light which travels from the second light source22-2 within a left range with respect to the front direction of thedisplay screen 11.

As shown in FIG. 15B, the third light source 22-3 positioned on theright when viewed from the front surface (light travel direction) isdisposed so that a center direction CD3 of the light source 22-3coincides with a third direction D3 which is line-symmetrical with thesecond direction D2 with respect to the reference direction SD as thesymmetry axis. In this embodiment, the third light source 22-3 isdisposed so that the center direction CD3 differs from the referencedirection SD by 60 degrees toward the right when viewed from the frontsurface. Therefore, the image sensor 18 according to this embodiment canreceive light which travels from the third light source 22-3 within aright range with respect to the front direction of the display screen11.

In the game system 10 according to this embodiment, since the player Pmoves along a floor (horizontal plane), it is preferable that the seconddirection D2 and the third direction D3 be parallel to the horizontalplane and differ in direction. When it is necessary to prevent lightemitted downward from the light sources 22-1 to 22-3 from beingreflected, the center directions CD1 to CD3 of the light sources 22-1 to22-3 may be adjusted upward from the horizontal direction HD by aboutfive degrees.

7. Functional Blocks

The configuration of the indication position calculation system (gamesystem) according to this embodiment is described below with referenceto FIG. 16. FIG. 16 is a functional block diagram showing an example ofthe indication position calculation system according to this embodiment.The indication position calculation system according to this embodimentmay have a configuration in which some of the elements (sections) shownin FIG. 16 are omitted.

An operation section 160 allows a player to input operation data. Inthis embodiment, the operation section 160 may be an indicator(controller, shooting device, or pointing device) configured so that theplayer can arbitrarily change the position and the direction of theoperation section 160 while holding the operation section 160 anddirects the operation section 160 toward an arbitrary position on theindication plane such as the display screen 11.

The operation section 160 includes a trigger as an operating section forthe player to perform an ON/OFF input. The operation section 160 mayinclude a button, a lever (analog pad), an arrow key, a steering wheel,a microphone, a touch panel display, or the like so that various typesof operation data can be input.

The operation section 160 includes an imaging section 162, adetermination section 164, and a calculation section 166.

The imaging section 162 may be implemented by an image sensor such as aCMOS sensor or a CCD camera. The imaging section 162 successivelyoutputs the light-reception information relating to each pixel from astarting pixel provided on one end of the acquired image to an end pixelprovided on the other end of the acquired image. The imaging section 162may successively output the light-reception information relating to eachpixel utilizing a hardware configuration, or may successively output thelight-reception information relating to each pixel under softwarecontrol.

The determination section 164 may be implemented by hardware such as aprocessor (e.g., CPU, MPU, or DSP) or an ASIC (e.g., gate array) and aprogram. The determination section 164 determines whether or not eachpixel satisfies a given condition based on the light-receptioninformation relating to each pixel successively output from the imagingsection 162.

The calculation section 166 may be implemented by hardware such as aprocessor (e.g., CPU, MPU, or DSP) or an ASIC (e.g., gate array) and aprogram. When the pixels which satisfy the given condition are pixelcorresponding to the light-emitting sections 13 and 14, the calculationsection 166 performs position calculations based on the identificationinformation relating to the pixels which satisfy the given condition tocalculate the indication position of the operation section 160.

The determination section 164 and the calculation section 166 may beintegrally implemented by one processor or the like. The determinationsection 164 and the calculation section 166 may be implemented by thefunction of a processing section 100 instead of providing thedetermination section 164 and the calculation section 166 in theoperation section 160.

A storage section 170 serves as a work area for the processing section100, a communication section 196, and the like. The function of thestorage section 170 may be implemented by a RAM (VRAM) or the like. Thestorage section 170 according to this embodiment includes a main storagesection 171 used as a work area, a frame buffer 172 in which the finaldisplay image and the like are stored, an object data storage section173 in which model data relating to an object is stored, a texturestorage section 174 in which the texture for each piece of object datais stored, and a Z buffer 176 in which a Z value is stored whengenerating an image of an object. Note that the storage section 170 mayhave a configuration in which some of these sections are omitted.

An information storage medium 180 (computer-readable medium) stores aprogram, data, and the like. The function of the information storagemedium 180 may be implemented by an optical disk (CD or DVD), amagneto-optical disk (MO), a magnetic disk, a hard disk, a magnetictape, a memory (ROM), or the like.

A program (data) for causing the processing section 100 to performvarious processes according to this embodiment is stored in theinformation storage medium 180. Specifically, a program which causes acomputer to function as each section according to this embodiment(program which causes a computer to perform the process of each section)is stored in the information storage medium 180.

A display section 190 outputs an image generated according to thisembodiment. The function of the display section 190 may be implementedby a CRT, an LCD, a touch panel display, or the like. In thisembodiment, a light-emitting unit 15 for calculating the relativepositions of the operation section 160 and the display screen of thedisplay section 190 is provided in or around the display screen of thedisplay section 190. In this embodiment, an infrared LED which emitsinvisible light is used as the light source of the light-emitting unit15.

A sound output section 192 outputs sound generated according to thisembodiment. The function of the sound output section 192 may beimplemented by a speaker, a headphone, or the like.

A portable information storage device 194 stores player's personal data,game save data, and the like. As the portable information storage device194, a memory card, a portable game device, and the like can be given.

The communication section 196 performs various types of control forcommunicating with the outside (e.g. host device or another imagegeneration system). The function of the communication section 196 may beimplemented by hardware such as a processor or a communication ASIC, aprogram, or the like.

The program (data) for causing a computer to function as each sectionaccording to this embodiment may be distributed to the informationstorage medium 180 (storage section 170) from an information storagemedium included in a host device (server) through a network and thecommunication section 196. Use of the information storage medium of thehost device (server) is also included within the scope of the invention.

The processing section 100 (processor) performs a game process, an imagegeneration process, a sound generation process, and the like based onoperation data from the operation section 160, a program, and the like.The game process includes starting a game when game start conditionshave been satisfied, proceeding with a game, disposing an object such asa character or a map, displaying an object, calculating game results,finishing a game when game end conditions have been satisfied, and thelike. The processing section 100 performs various processes using thestorage section 170 as a work area. The function of the processingsection 100 may be implemented by hardware such as a processor (e.g. CPUor DSP) or an ASIC (e.g. gate array) and a program.

The processing section 100 according to this embodiment includes adisplay control section 104, a determination section 106, an evaluationsection 108, a drawing section 120, and a sound generation section 130.Note that the processing section 100 may have a configuration in whichsome of these sections are omitted.

The display control section 104 performs a display control process on anobject displayed on the display section 190. Specifically, the displaycontrol section 104 performs the display control process such asgenerating an object (e.g. character, background, target, car, ball,item, building, tree, pillar, wall, or map), directing the displayposition of an object, or causing an object to disappear. Specifically,the display control section 104 performs the display control processsuch as registering a generated object in an object list, transferringthe object list to the drawing section 120 and the like, or deleting adisappeared object from the object list. The display control section 104displays an object indicating the indication position (impact position)on the display screen 11 based on information relating to the indicationposition of the operation section 160 on the display screen 11.

The determination section 106 determines the positional relationshipbetween the indication position information relating to the operationsection 160 on the display screen 11 of the display section 190 and atarget object TO based on an operation input using the operating section(trigger) provided in the operation section 160. Specifically, thedetermination section 106 determines whether or not the indicationposition has hit (coincides with or reaches) the display position of thetarget object TO based on the indication position information when theoperation input using the operating section has been received.

The evaluation section 108 evaluates the operation using the operationsection 160 based on the hit determination result. In this embodiment,the evaluation section 108 evaluates the operation of the operator bymeans of score calculation and the like when the target object TO hasbeen hit.

The drawing section 120 performs a drawing process based on the resultsof various processes (game process) performed by the processing section100 to generate an image, and outputs the generated image to the displaysection 190. An image generated by the drawing section 120 may be atwo-dimensional image or a three-dimensional image. When generating athree-dimensional image, the drawing section 120 performs a geometricprocess such as coordinate transformation (world coordinatetransformation or camera coordinate transformation), clipping, orperspective transformation, and creates drawing data (e.g. primitivesurface vertex coordinates, texture coordinates, color data, normalvector, and alpha-value) based on the processing results. The drawingsection 120 draws an object (one or more primitives) subjected toperspective transformation (geometric process) in a drawing buffer(buffer which can store image information in pixel units such as a framebuffer or intermediate buffer; VRAM) based on the drawing data(primitive data). This causes an image viewed from a virtual camera(given view point) to be generated in a game space.

The sound generation section 130 performs a sound process based on theresults of various processes performed by the processing section 100 togenerate game sound such as background music (BGM), effect sound, orvoice, and outputs the generated game sound to the sound output section192.

The image generation system according to this embodiment may beconfigured as a system dedicated to a single-player mode in which onlyone player can play a game, or a system which also implements amulti-player mode in which a plurality of players can play a game.

When a plurality of players play a game, a game image and game soundprovided to the players may be generated using one terminal, or may begenerated by a distributed process using a plurality of terminals (gamedevices or portable telephones) connected via a network (transmissionline or communication line), for example.

The invention is not limited to the above-described embodiments, andvarious modifications can be made within the scope of the invention. Forinstance, any term cited together with a different term having a broadermeaning or the same meaning at least once in this specification ordrawings can be replaced by the different term in any place in thisspecification and drawings.

The above description has been given taking an example in which thelight-emitting unit 15 includes two light-emitting sections 13 and 14independently provided. Note that the light-emitting unit 15 may beformed by integrating the two light-emitting sections 13 and 14. Forexample, the light-emitting unit 15 may be formed as an oblongrod-shaped member, and the light-emitting sections 13 and 14 may bedisposed on the right and left ends. The distance between thelight-emitting sections 13 and 14 may be changed in stages in adirection indicated by an arrow. For example, the distance between thelight-emitting sections 13 and 14 may be changed in stages correspondingto monitors ranging from a 20-inch monitor to a 50-inch monitor.

The above description has been given taking an example in which thelight source 22 emits infrared light (i.e., invisible light). Note thatthe light source 22 may emit another type of invisible light or may emitvisible light. A light source which emits invisible light and a lightsource which emits visible light may be provided so that the lightsources can be switched. In particular, visible light may be output whenthe operator indicates the indication plane in order to initialize thepositional relationship between the light-emitting section (lightsource) and the indicator (light-receiving section).

The invention may be applied to various image generation systems. Theabove embodiments have been described taking an example of applying theinvention to a game system. Note that the invention may also applied toan indication position calculation system including a presentationsystem and the like and an indicator used for an indication positioncalculation system.

The invention may be applied to various image generation systems such asan arcade game system, a consumer game system, a large-scale attractionsystem in which a number of players participate, a simulator, amultimedia terminal, a system board which generates a game image, and aportable telephone.

Although only some embodiments of this invention have been described indetail above, those skilled in the art will readily appreciate that manymodifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of this invention.Accordingly, all such modifications are intended to be included withinthe scope of the invention.

1. An indication position calculation system calculating an indicationposition of an indicator, the indication position calculation systemcomprising: a light-emitting section; an imaging section which isprovided in the indicator, acquires an image and successively outputslight-reception information of pixels of the acquired image, wherein oneof the pixels having the light-reception information output primarily isdisposed on a lower side of the image and another one of the pixelshaving the light-reception information output last is disposed on anupper side of the image when the indicator is held in a referenceposition; a determination section which determines whether or not thepixels are effective pixels satisfying a given condition based on thelight-reception information; and a calculation section which performsposition calculations based on identification information of theeffective pixels in order to obtain the indication position of theindicator when light received by the effective pixels is included inlight emitted from the light-emitting section, the calculation sectionperforming the position calculations based on the identificationinformation of a first effective pixel which is one of the effectivepixels and is primarily determined to satisfy the given condition. 2.The indication position calculation system as defined in claim 1,wherein the calculation section sets a predetermined area of the imageincluding the first effective pixel as a determination area, andperforms the position calculations based on the identificationinformation of part of the effective pixels included in thedetermination area.
 3. The indication position calculation system asdefined in claim 2, comprising: a plurality of the light-emittingsections having a predetermined positional relationship with each other,wherein the calculation section sets a predetermined area of the imageincluding the first effective pixel as a first determination area, setsanother predetermined area of the image including a second effectivepixel which has been primarily determined to satisfy the given conditionamong the pixels out of the first determination area as a seconddetermination area, and then performs the position calculations based onthe identification information of the effective pixels within the firstdetermination area and the second determination area.
 4. The indicationposition calculation system as defined in claim 2, wherein thedetermination section determines whether or not each of the pixelssatisfies a first condition and then determines whether or not each ofthe pixels satisfies a second condition; and wherein the calculationsection calculates a representative value of the determination areabased on the identification information of the effective pixels and thenperforms the position calculations based on the representative value,while making weight on the identification information of the effectivepixels included in the determination area and satisfying the secondcondition different from weight on the identification information of theeffective pixels included in the determination area but not satisfyingthe second condition.
 5. The indication position calculation system asdefined in claim 1, wherein the light-emitting section emits light in apredetermined wavelength band; and wherein the imaging section has alight reception sensitivity for light including the predeterminedwavelength band.
 6. The indication position calculation system asdefined in claim 1, further comprising: a shielding section provided inthe light-emitting section and shielding part of light from thelight-emitting section emitted downward in a predetermined degrees ofangle or less from the horizontal.
 7. The indication positioncalculation system as defined in claim 6, wherein the shielding sectionis disposed at a position enabling the shielding section to shield partof the light from the light-emitting section emitted downward from thehorizontal so that no reflected light from lower space enters theimaging section when the light-emitting section and the imaging sectionhave a given reference positional relationship.
 8. The indicationposition calculation system as defined in claim 1, wherein thelight-emitting section is directed in a direction enabling to preventlight from the light-emitting section from being emitted downward fromthe horizontal so that no reflected light from lower space enters theimaging section when the light-emitting section and the imaging sectionhave a given reference positional relationship.
 9. The indicationposition calculation system as defined in claim 1, further comprising: afilter which is provided in the indicator and through which light in thesame wavelength band as light from the light-emitting section is allowedto pass toward the imaging section.
 10. The indication positioncalculation system as defined in claim 1, comprising: a plurality of thelight-emitting sections having a predetermined positional relationshipwith each other, wherein the calculation section performs the positioncalculations based on the identification information of the effectivepixels corresponding to each of the light-emitting sections.
 11. Anindicator for an indication position calculation system, the indicatorcomprising: an imaging section which acquires an image of a lightemitting section and successively outputs light-reception information ofpixels of the acquired image; a determination section which determineswhether or not the pixels are effective pixels satisfying a givencondition based on the light-reception information; and a calculationsection which performs position calculations based on identificationinformation of the effective pixels in order to obtain an indicationposition of the indicator when light received by the effective pixels isincluded in light emitted from the light-emitting section, thecalculation section performing the position calculations based on theidentification information of a first effective pixel which is one ofthe effective pixels and is primarily determined to satisfy the givencondition; and the imaging section being provided in the indicator heldin a reference position when one of the pixels having thelight-reception information output primarily is disposed on a lower sideof the image and another one of the pixels having the light-receptioninformation output last is disposed on an upper side of the image.
 12. Agame system calculating an indication position of an indicator, the gamesystem comprising: a display section which displays an object; alight-emitting section which has a given positional relationship withthe display section; an imaging section which is provided in theindicator, acquires an image and successively outputs light-receptioninformation of pixels of the acquired image, wherein one of the pixelshaving the light-reception information output primarily is disposed on alower side of the image and another one of the pixels having thelight-reception information output last is disposed on an upper side ofthe image when the indicator is held in a reference position; adetermination section which determines whether or not the pixels areeffective pixels satisfying a given condition based on thelight-reception information; and a calculation section which performsposition calculations based on identification information of theeffective pixels in order to obtain the indication position of theindicator when light received by the effective pixels is included inlight emitted from the light-emitting section, the calculation sectionperforming the position calculations based on the identificationinformation of a first effective pixel which is one of the effectivepixels and is primarily determined to satisfy the given condition. 13.An indication position calculation method comprising: causing an imagingsection provided in an indicator to acquire an image of a light emittingsection and successively output light-reception information of pixels ofthe acquired image; causing a determination section to determine whetheror not the pixels are effective pixels satisfying a given conditionbased on the light-reception information; and causing a calculationsection to perform position calculations based on identificationinformation of the effective pixels in order to obtain an indicationposition of the indicator when light received by the effective pixels isincluded in light emitted from the light-emitting section, thecalculation section performing the position calculations based on theidentification information of a first effective pixel which is one ofthe effective pixels and is primarily determined to satisfy the givencondition; and the imaging section being provided in the indicator heldin a reference position when one of the pixels having thelight-reception information output primarily is disposed on a lower sideof the image and another one of the pixels having the light-receptioninformation output last is disposed on an upper side of the image.